The present invention relates generally to signal processors for use in processing video data, and the like, and more particularly to signal processors for use with multi-sensor imaging systems, such as forward looking infrared imaging systems, and the like, which provide electronically enhanced video images displayed on a video monitor.
Conventional forward looking infrared (FLIR) sensor systems, and the like, are employed as night vision systems on aircraft, tanks, ships and other military vehicles. The conventional FLIR system for example, comprises a sensor system, a signal processor and a video display. The sensor comprises a large number of detectors whose signal outputs are multiplexed and applied to the signal processor. The signal processor electronically demultiplexes, enhances and converts the sensor signals into video signals compatible with the video display, and applies the enhanced video signals to the display for viewing by the vehicle operator.
Although all FLIR systems incorporate signal processors, the sophistication and image enhancement capabilities vary widely from system to system. For example, prior art systems have typically incorporated responsivity equalization circuitry, automatic gain control circuitry and video compacting circuitry. However, these prior art systems have employed analog circuits to accomplish the gain control and video compacting functions, and have incorporated manually operated potentiometers to implement the responsivity equalization function The use of manually-calibrated, analog systems in prior art FLIR signal processors, and the like, has resulted in less than optimum performance from these systems.
Although relating generally to staring focal plane detector arrays, a publication entitled "Reference-free nonuniformity compensation for IR imaging arrays," SPIE, vol. 252, Smart Sensors II, 1980, pp, 10-17 discusses some conventional infrared signal processing problems and describes a reference-free compensation scheme to accomplish automatic responsivity equalization. The compensation scheme described in this paper utilizes scene statistics to develop signals suitable for implementing temperature compensation.